<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
<script>
  // 简单数据类型 BigInt()
  // 构造函数， 代码可读性
const wes = Symbol('Wes');
const person = Symbol('Wes');
// console.log(wes == person);
const classRoom = {
  [Symbol('Mark')]: { grade: 50, gender: 'male'},
  [Symbol('oliva')]: { grade: 80, gender: 'female' },
  [Symbol('oliva')]: { grade: 85, gender: 'female'},
  "dl": ["国文", "陈倩文"]
} 
// console.log(classRoom);
// for key in 
// symbol key 不可以被枚举
for (const person in classRoom) {
  console.log(person, '////')
}

const syms = Object.getOwnPropertySymbols(classRoom);
console.log(syms);
const data = syms.map(sym => classRoom[sym]);
console.log(data);
</script>
</body>
</html>